Powder coating having good UV resistance

ABSTRACT

Provided are thermosetting powder coatings based on a resin based on dimethyl 2,6-decalindicarboxylate and neopentyl glycol. The resin may be modified with other diacids or diols but must have a suitable glass transition temperature (Tg) required for powder coatings. We have found that this aliphatic polyester meets the basic Tg requirement of powder coatings and found that it provides powder coating with excellent weatherability. The polyester resin has a number average molecular weight (Mn) of from about 1,500 to about 10,000, a glass transition temperature (Tg) of about 45° C. to 100° C., and a hydroxyl or acid number of from about 20 to about 100.

FIELD OF THE INVENTION

This invention belongs to the field of powder coatings. In particular,this invention relates to weatherable thermosetting powder coatingsbased preferably on resins comprised of dimethyl2,6-decalindicarboxylate and neopentyl glycol.

BACKGROUND OF THE INVENTION

Plastic materials used in the manufacture of powder coatings areclassified broadly as either thermosetting or thermoplastic. In theapplication of thermoplastic powder coatings, heat is applied to thecoating on the substrate to melt the particles of the powder coating andthereby permit the particles to flow together and form a smooth coating.

Thermosetting coatings, when compared to coatings derived fromthermoplastic compositions, generally are tougher, more resistant tosolvents and detergents, have better adhesion to metal substrates and donot soften when exposed to elevated temperatures.

Resins which exhibit good weatherability and meet the basic Tg (glasstransition temperature) requirements for powder coating compositions arebecoming increasingly important, particularly for outdoor applications.

Powder coatings based on acrylic resins are known to have excellentweathering performance but are generally more expensive.

British Patent No. 962,913 discloses polyesters containingcyclohexanedicarboxylic acid (CHDA) and 2,6-decalindimethanol useful asfilm and molding plastics.

U.S. Pat. No. 3,313,777 discloses polyesters containing CHDA and2,2,4,4-tetramethyl-1,3-cyclobutanediol useful as film and moldingplastics.

U.S. Pat. No. 4,363,908 discloses copolyesters containing CHDA and2,2,4,4-tetramethyl-1,3-cyclobutanediol useful as adhesives.

U.S. Pat. No. 4,525,504 discloses stabilized polyesters with improvedweatherability based on CHDA and2,2,4,4-tetramethyl-1,3-cyclobutanediol. These polyesters are highmolecular weight polyesters useful in molding plastics.

U.S. Pat. No. 5,097,006 discloses all-aliphatic polyester resins basedon 1,4-cyclohexanedicarboxylic acid and hydrogenated bisphenol A and/orcycloaliphatic diols, useful as weatherable powder coating resins.

Powder coatings which exhibit good weatherability and meet the basic Tg(glass transition temperature) requirements for a thermosetting powdercoating composition are becoming increasingly important, particularlyfor outdoor applications. We have found that polyester resins based ondimethyl 2,6-decalindicarboxylate and neopentyl glycol meet the basic Tgrequirement for powder coatings and can be formulated with a crosslinkerinto powder coatings having excellent weatherability.

SUMMARY OF THE INVENTION

This invention relates to thermosetting powder coatings based on a resinprepared from dimethyl 2,6-decalindicarboxylate and neopentyl glycol.

The resin may be modified with other diacids or diols but must have a Tgsuitable for powder coatings. We have found that this aliphaticpolyester meets the basic Tg requirement of powder coatings and foundthat it provides powder coating with excellent weatherability. Thepolyester resin has a number average molecular weight (Mn) of from about1,500 to about 10,000, preferably from about 2,000 to 6,000 and a glasstransition temperature (Tg) of about 45° C. to 100° C., preferably 50°to 70° C. and hydroxyl or acid number of from about 20 to about 100,preferably from about 30 to about 80.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a curable polyester comprising

(a) about 40 to about 100 mole percent of residues of2,6-decalindicarboxylic acid;

(b) about 40 to about 100 mole percent of residues of2,2-dimethyl-1,3-propanediol;

and any remaining residues comprised of residues of polyols andpolycarboxylic acids;

said polyester having a number average molecular weight of from about1500 to 10,000, a glass transition temperature of about 45° C. to about100° C., and a hydroxy or acid number of from 20 to 100.

In the above polyester, it should be appreciated that the total molepercent of (a) and polycarboxylic acids will always equal 100 percent;likewise, the total mole percent of (b) and polyols will always equal100 percent.

The above polyesters are useful as binders in thermosetting powdercoating compositions. As noted above, the polyesters contain 40 to about100 mole percent of residues of 2,6-decalindicarboxylic acid and 40 to100 mole percent of resides of 2,2-dimethyl-1,3-propanediol, with 70 to100 and 70 to 100 being preferred, respectively. In a further preferredembodiment, the polyester will have from about 80 to about 100 molepercent of residues of 2,6-decalindicarboxylic acid and 80 to 100 molepercent of resides of 2,2-dimethyl-1,3-propanediol.

In the above polyesters, the remaining percent of dicarboxylic acid andpolyol residues can be selected from other known aliphatic polyol andaliphatic diacid residues.

Examples of such polyols includes polyester polyol branching agents suchas trimethylolpropane, trimethylolethane, glycerol, and the like. Otherexamples of suitable polyols include 1,4-butanediol, ethylene glycol,propylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol,2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol,1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, thiodiethanol, 1,2-,1,3- and 1,4-cyclohexanedimethanol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, hydrogenated Bisphenol A,1,4-xylylene-diol and the like.

Preferably the other dicarboxylic acid residues of the polyesters areselected from residues of oxalic; malonic, dimethylmalonic; succinic;glutaric; adipic; trimethyladipic; pimelic, 2,2-dimethylglutaric;azelaic; sebacic; fumaric; maleic; itaconic;1,3-cyclopentanedicarboxylic; 1,2-cyclohexanedicarboxylic;1,3-cyclohexanedicarboxylic; 1,4-cyclohexanedicarboxylic; phthalic;terephthalic; isophthalic; 2,5-norbornanedicarboxylic; 1,4-naphthalic;diphenic; 4,4'-oxydibenzoic, diglycolic; thiodipropionic;4,4'-sulfonyldibenzoic; and 2,6-naphthalenedicarboxylic acids.

As used herein, the terms "hydroxyl-functional" and"carboxyl-functional" as used to describe the polyester is used in itsordinary art-recognized meaning. In other words, such terms denotewhether the polyester (or binder) is predominantly carboxyl- orhydroxyl-functional in character, thereby dictating the choice ofcrosslinker. In such a case, for example, a hydroxyl functional resinwill have an acid number of less than about 15 (and a hydroxyl number of20 to 100) and a carboxyl functional resin will have a hydroxyl numberof less than about 15 (and a carboxyl or acid number of 20 to 100).

As a further aspect of the present invention, there is provided athermosetting powder coating composition comprising

(I) a curable polyester comprising

(a) about 40 to about 100 mole percent of residues of2,6-decalindicarboxylic acid;

(b) about 40 to about 100 mole percent of residues of2,2-dimethyl-1,3-propanediol;

and any remaining residues comprised of residues of polyols andpolycarboxylic acids;

said polyester having a number average molecular weight of from about1500 to 10,000, a glass transition temperature of about 45° C. to about100° C., and a hydroxy or acid number of from 20 to 100;

(II) a crosslinking effective amount of a cross-linker reactive withsaid polyester.

In a preferred embodiment, the thermosetting powder coating compositionof the present invention is comprised of

A. a carboxyl polyester resin,

B. a weatherable epoxy crosslinker such as triglycidylisocyanurate(TGIC) commercially available as Aradite PT-810 by Ciba Geigy or aBeta-hydroxylalkyl amide such as Bis(N,N-dihydroxyethyl)adipamidecommercially available from Rohm and Haas as Primid XL552 or

A. a hydroxyl polyester resin described above

B. a blocked polyisocyanate crosslinker or a crosslinker from theglycoluril family of "aminoplast" crosslinking agent, such astetramethoxymethyl glycouril commercially available as Powderlink 1174.

The blocked polyisocyanate crosslinkers are those well known in the artof powder coatings.

Examples include those which are based on caprolactam blockedisophoronediisocyanates such as Huls B1530, Cargill 2400, Rucote NI-2 orthose which are based on caprolactam-blocked tolylene 2,4-diisocyanatesuch as commercial Cargill 2450 crosslinker or the self blockeduretdione of isophoronediisocyanate commercially available as HulsBF1540, and

C. additives such as benzoin, flow aids, pigments and catalyst.

Additives commonly used are benzoin for reducing entrapped air orvolatiles, flow aid such as Modaflow III, catalyst such as dibutyltindilaurate and pigments such as titanium dioxide.

In a further preferred embodiment, the curable polyester is comprised of

(a) 40 to 100 mole percent of residues of 2,6-decalindicarboxylic acid;0 to 60 mole percent of residues of a compound selected from the groupconsisting of naphthalenedicarboxylic acid, isophthalic acid,terephthalic acid, and cyclohexanedicarboxylic acid; and

(b) 40 to 100 mole percent of residues of 2,2-dimethyl-1,3-propanediol;0 to 50 mole percent of residues of cyclohexanedimethanol; 0 to 10 molepercent of residues of a compound selected from the group consisting oftrimethylolpropane, glycerol, and trimellitic anhydride;

the total mole percent of (a) being 100 percent and the total molepercent of (b) being 100 percent.

In the compositions of the present invention, the mostreadily-available, and thus the preferred, blocked isocyanatecross-linking agents or compounds are those commonly referred to asε-caprolactam-blocked isophorone diisocyanate, e.g., those described inU.S. Pat. Nos. 3,822,240, 4,150,211 and 4,212,962, incorporated hereinby reference. However, the products marketed as ε-caprolactam-blockedisophorone diisocyanate may consist primarily of the blocked,difunctional, monomeric isophorone diisocyanate, i.e., a mixture of thecis and trans isomers of3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, the blocked,difunctional dimer thereof, the blocked, trifunctional trimer thereof ora mixture of the monomeric, dimeric and/or trimeric forms. For example,the blocked polyisocyanate compound used as the cross-linking agent maybe a mixture consisting primarily of the ε-caprolactam-blocked,difunctional, monomeric isophorone diisocyanate and theε-caprolactam-blocked, trifunctional trimer of isophorone diisocyanate.The description herein of the cross-linking agents as "blockedisocyanates" refers to compounds which contain at least two isocyanatogroups which are blocked with, i.e., reacted with, another compound,e.g., ε-caprolactam. The reaction of the isocyanato groups with theblocking compound is reversible at elevated temperatures, e.g., normallyabout 150° C., and above, at which temperature the isocyanato groups areavailable to react with the hydroxyl groups present on the free hydroxygroups of the polyester to form urethane linkages.

Alternatively, the blocked isocyanate may be a cross-linking effectiveamount of an adduct of the 1,3-diazetidine-2,4-dione dimer of isophoronediisocyanate and a diol having the structure ##STR1## wherein R¹ is adivalent 1-methylene-1,3,3-trimethyl-5-cyclohexyl radical, i.e., aradical having the structure ##STR2## R² is a divalent aliphatic,cycloaliphatic, araliphatic or aromatic residue of a diol; and X is a1,3-diazetidine-2,4-dionediyl radical, i.e., a radical having thestructure ##STR3## wherein the ratio of NCO to OH groups in theformation of the adduct is about 1:0.5 to 1:0.9, the mole ratio ofdiazetidinedione to diol is from 2:1 to 6:5, the content of freeisocyanate groups in the adduct is not greater than 8 weight percent andthe adduct has a molecular weight of about 500 to 4000 and a meltingpoint of about 70° to 130° C.

The adducts of the 1,3-diazetidine-2,4-dione dimer of isophoronediisocyanate and a diol are prepared according to the proceduresdescribed in U.S. Pat. No. 4,413,079, incorporated herein by reference,by reacting the diazetidine dimer of isophorone diisocyanate, preferablyfree of isocyanurate trimers of isophorone diisocyanate, with diols in aratio of reactants which gives as isocyanto:hydroxyl ratio of about1:0.5 to 1:0.9, preferably 1:0.6 to 1:0.8. The adduct preferably has amolecular weight of 1450 to 2800 and a melting point of about 85 to 120°C. The preferred diol reactant is 1,4-butanediol. Such an adduct iscommercially available under the name Huls BF1540.

In the β-hydroxylalkyl amide systems above, it is further preferred thata catalyst comprised of a carboxylate salt of a metal such as zinc,aluminum, or titanium, or an oxide of aluminum or zinc is present.Especially preferred as a catalyst is zinc stearate. Further descriptionof catalyst systems for an activated β-hydroxylalkyl amide system can befound in U.S. application Ser. No. 08/084,104, incorporated herein byreference.

The amount of the blocked isocyanate cross-linking compound (or othercrosslinker) present in the compositions of this invention can be varieddepending on several factors such as those mentioned above relative tothe amount of component (I) which is utilized and its hydroxyl number.Typically, the amount of cross-linking compound which will effectivelycross-link the polymers to produce coatings having a good combination ofproperties is in the range of about 5 to 30 weight percent, preferably15 to 25 weight percent, based on the total weight of components (I) and(II).

The powder coating compositions of this invention may be prepared fromthe compositions described herein by dry-mixing and then melt-blendingcomponents (I) and (II), and optionally a cross-linking catalyst, alongwith other additives commonly used in powder coatings, and then grindingthe solidified blend to a particle size, e.g., an average particle sizein the range of about 10 to 300 microns, suitable for producing powdercoatings. For example, the ingredients of the powder coating compositionmay be dry blended and then melt blended in a Brabender extruder at 90°to 130° C., granulated and finally ground. The melt blending should becarried out at a temperature sufficiently low to prevent the unblockingof the polyisocyanate cross-linking compound and thus avoiding prematurecross-linking.

The powder coating compositions preferably contain a flow aid, alsoreferred to as flow control or leveling agents, to enhance the surfaceappearance of cured coatings of the powder coating compositions. Suchflow aids typically comprise acrylic polymers and are available fromseveral suppliers, e.g., MODAFLOW from Monsanto Company and ACRONAL fromBASF. Other flow control agents which may be used include Modarez MFPavailable from SYNTHRON, EX 486 available from Troy Chemical, BYK 360Pavailable from BYK Mallinkrodt and PERENOL F-30-P available from Henkel.An example of one specific flow aid is an acrylic polymer having amolecular weight of about 17,000 and containing 60 mole percent2-ethylhexyl methacrylate residues and about 40 mole percent ethylacrylate residues. The amount of flow aid present may preferably be inthe range of about 0.5 to 4.0 weight percent, based on the total weightof the resin component, and the cross-linking agent.

The powder coating compositions may be deposited on various metallic andnon-metallic (e.g., thermoplastic or thermoset composite) substrates byknown techniques for powder deposition such as by means of a powder gun,by electrostatic deposition or by deposition from a fluidized bed. Influidized bed sintering, a preheated article is immersed into asuspension of the powder coating in air. The particle size of the powdercoating composition normally is in the range of 60 to 300 microns. Thepowder is maintained in suspension by passing air through a porousbottom of the fluidized bed chamber. The articles to be coated arepreheated to about 250° to 400° F. (about 121° to 205° C.) and thenbrought into contact with the fluidized bed of the powder coatingcomposition. The contact time depends on the thickness of the coatingthat is to be produced and typically is from 1 to 12 seconds. Thetemperature of the substrate being coated causes the powder to flow andthus fuse together to form a smooth, uniform, continuous, uncrateredcoating. The temperature of the preheated article also effectscross-linking of the coating composition and results in the formation ofa tough coating having a good combination of properties. Coatings havinga thickness between 200 and 500 microns may be produced by this method.

The compositions also may be applied using an electrostatic processwherein a powder coating composition having a particle size of less than100 microns, preferably about 15 to 50 microns, is blown by means ofcompressed air into an applicator in which it is charged with a voltageof 30 to 100 kV by high-voltage direct current. The charged particlesthen are sprayed onto the grounded article to be coated to which theparticles adhere due to the electrical charge thereof. The coatedarticle is heated to melt and cure the powder particles. Coatings of 40to 120 microns thickness may be obtained.

Another method of applying the powder coating compositions is theelectrostatic fluidized bed process which is a combination of the twomethods described above. For example, annular or partially annularelectrodes are mounted in the air feed to a fluidized bed so as toproduce an electrostatic charge such as 50 to 100 kV. The article to becoated, either heated, e.g., 250° to 400° F., or cold, is exposedbriefly to the fluidized powder. The coated article then can be heatedto effect cross-linking if the article was not preheated to atemperature sufficiently high to cure the coating upon contact of thecoating particles with the article.

The powder coating compositions of this invention may be used to coatarticles of various shapes and sizes constructed of heat-resistancematerials such as glass, ceramic and various metal materials. Thecompositions are especially useful for producing coatings on articlesconstructed of metals and metal alloys, particularly steel articles.

Further examples of formulation methods, additives, and methods ofpowder coating application may be found in User's Guide to PowderCoating, 2nd Ed., Emery Miller, editor, Society of ManufacturingEngineers, Dearborn, (1987).

The inherent viscosity (I.V.), in dL/g are determined inphenol/tetrachloroethane (60/40 w/w) at a concentration of 0.5 g/100 ml.

The resin melt viscosity, in poise, are determined using an ICI meltviscometer at 200° C.

The acid number and hydroxyl number are determined by titration andreported as mg of KOH consumed for each gram of resin.

The glass transition temperature (Tg), is determined by differentialscanning calorimetry (DSC) on the second heating cycle scanning at 20°C./minute after the sample has been heated to melt and quenched to belowthe resin Tg. Tg values are reported as midpoint.

The weight average molecular weight (Mw) and number average molecularweight (Mn) are determined by gel permeation chromatography intetrahydrofuran (THF) using polystyrene standard and a UV detector.

Impact strengths are determined using a Gardner Laboratory, Inc., impacttester per ASTM D 2794-84.

Pencil hardness is determined using ASTM D 3363-74. The hardness isreported as the hardest pencil which will not cut into the coating. Theresults are expressed according to the following scale: (softest) 6B,5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H (hardest).

The 20 and 60 degree gloss are measured using a gloss meter (GardenerLaboratory, Inc. Model GC-9095) according to ASTM D-523.

The QUV resistance is measured by the loss of gloss. QUV is run byalternately exposing the coated panel at 45° C. to a 313 nm fluorescenttube for 8 hours followed by a condensation at 45° C. for 4 hours. Glossis monitored every 100 hours of exposure. The number of hours needed toreduce the gloss to 50% of the original is reported.

The coatings provided this invention are further illustrated by thefollowing examples.

EXAMPLE 1

To a 500 ml, 3-neck round bottom flask were added dimethyl2,6-decalindicarboxylate (191.1 g, 0.752 moles), neopentyl glycol (69.8g, 0.67 moles), hydrogenated bisphenol A (30.2 g, 0.126 moles),trimethylolpropane (5.6 g, 0.042 moles) and 100 ppm Titanium and IRGANOX1010 antioxidant (Ciba Geigy) (0.25 g). The contents were heated to meltat 180° C. The flask was swept with 1.0 standard cubic feet per hour(scfh) nitrogen while the temperatures was raised from 180° C. to 230°C. over a 6-hour period. The batch temperature was maintained at 230° C.for 8 hours. The molten resin was poured to a syrup can where it cooledto a solid with the following properties:

    ______________________________________                                        I.V., (dL/g)       0.202                                                      ICI Melt Viscosity at                                                                            7                                                          200° C. (poise)                                                        Acid Number        0.0                                                        Hydroxyl number    39                                                         DSC (2nd cycle)                                                               Tg, (°C.)   61                                                         ______________________________________                                    

EXAMPLE 2

To a 500 ml, 3-neck round bottom flask were added dimethyl2,6-decalindicarboxylate (198.2 g, 0.780 moles), neopentyl glycol (63.2g, 0.61 moles), 1,4-cyclohexanedimethanol (31.2 g, 0.217 moles),trimethylolpropane (5.8 g, 0.043 moles) and 100 ppm Titanium and IRGANOX1010 antioxidant (0.25 g). The contents were heated to melt at 180° C.The flask was swept with 1.0 scfh nitrogen while the temperatures wasraised from 180° C. to 230° C. over a 6-hour period. The batchtemperature was maintained at 230° C. for 8 hours. The molten resin waspoured to a syrup can where it cooled to a solid with the followingproperties:

    ______________________________________                                        I.V., (dL/g)       0.212                                                      ICI Melt Viscosity at                                                                            7                                                          200° C. (poise)                                                        Acid Number        0.0                                                        Hydroxyl number    33                                                         DSC (2nd cycle)                                                               Tg, (°C.)   48                                                         ______________________________________                                    

EXAMPLE 3

To a 500 ml, 3-neck round bottom flask were added2,6-naphthalenedicarboxylic acid (175.23 g, 0.78 moles), neopentylglycol (76.2 g, 0.73 moles), hydrogenated bisphenol A (20.7 g, 0.086moles), trimethylolpropane (5.8 g, 0.043 moles) and FASCAT 4100 catalyst(0.25 g) and IRGANOX 1010 (0.25 g). The contents were heated to melt at180° C. The flask was swept with 1.0 scfh nitrogen while thetemperatures was raised from 180° C. to 230° C. over a 6-hour period.The batch temperature was maintained at 230° C. for 8 hours. The moltenresin is poured to a syrup can where it cooled to a solid with thefollowing properties:

    ______________________________________                                        I.V., (dL/g)       0.205                                                      ICI Melt Viscosity at                                                                            16                                                         200° C. (poise)                                                        Acid Number        1.0                                                        Hydroxyl number    37                                                         DSC (2nd cycle)                                                               Tg, (°C.)   57                                                         ______________________________________                                    

EXAMPLE 4

A powder coating composition was prepared from the following materials:

    ______________________________________                                        164.0 g         Polyester of Example 1                                        36.0 g          HULS 1530 crosslinker                                         100.0 g         Titanium dioxide                                              2.0             Dibutyltin dilaurate                                          3.0 g           MODAFLOW 2000                                                 2.0 g           Benzoin                                                       2.0 g           TINUVIN 144                                                   4.0 g           TINUVIN 234                                                   ______________________________________                                    

The above material was mixed in a Vitamix mixer and compounded in an APVextruder at 110° C. The extrudate was cooled, granulated, and pulverizedin a Bantam mill with liquid nitrogen bled into the grinding chamber.The powder was classified through a 200 mesh screen.

The powder was electrostatically applied to a 3 in. X 9 in. metal paneland cured in a 350° F. oven for 20 minutes. The film properties are asfollows:

    ______________________________________                                        Film thickness, Mil       2.0                                                 Impact strength, (in.-lb)                                                     Front                    20                                                   Reverse                 <20                                                   Pencil Hardness           2H                                                  Gloss                                                                         20 deg                   28                                                   60 deg                   80                                                   MEK double rubs          200+                                                 ______________________________________                                    

EXAMPLE 5

A powder coating composition was prepared from the following materials:

    ______________________________________                                        168.0 g         Polyester of Example 2                                        32.0 g          HULS 1530 crosslinker                                         100.0 g         Titanium dioxide                                              2.0             Dibutyltin dilaurate                                          3.0 g           MODAFLOW 2000                                                 2.0 g           Benzoin                                                       2.0 g           TINUVIN 144                                                   4.0 g           TINUVIN 234                                                   ______________________________________                                    

The above material was mixed in a Vitamix mixer and compounded in an APVextruder at 110° C. The extrudate was cooled, granulated, and pulverizedin a Bantam mill with liquid nitrogen bled into the grinding chamber.The powder was classified through a 200 mesh screen.

The powder was electrostatically applied to a 3 in. X 9 in. metal paneland cured in a 350° F. oven for 20 minutes. The film properties are asfollows:

    ______________________________________                                        Film thickness, Mil       2.1                                                 Impact strength, (in.-lb)                                                     Front                    20                                                   Reverse                 <20                                                   Pencil Hardness         F                                                     Gloss                                                                         20 deg                   62                                                   60 deg                   94                                                   *MEK double rubs         200+                                                 QUV, hours to 50% loss  1500                                                  ______________________________________                                         *(Methyl Ethyl Ketone)                                                   

EXAMPLE 6

A powder coating composition was prepared from the following materials:

    ______________________________________                                        164.0 g         Polyester of Example 3                                        36.0 g          HULS 1530 crosslinker                                         100.0 g         Titanium dioxide                                              2.0             Dibutyltin dilaurate                                          3.0 g           MODAFLOW 2000                                                 2.0 g           Benzoin                                                       2.0 g           TINUVIN 144                                                   4.0 g           TINUVIN 234                                                   ______________________________________                                    

The above material was mixed in a Vitamix mixer and compounded in an APVextruder at 110° C. The extrudate was cooled, granulated, and pulverizedin a Bantam mill with liquid nitrogen bled into the grinding chamber.The powder was classified through a 200 mesh screen.

The powder was electrostatically applied to a 3 in. X 9 in. metal paneland cured in a 350° F. oven for 20 minutes. The film properties are asfollows:

    ______________________________________                                        Film thickness, Mil       2.2                                                 Impact strength, (in.-lb)                                                     Front                    20                                                   Reverse                 <20                                                   Pencil Hardness         H                                                     Gloss                                                                         20 deg                   52                                                   60 deg                   90                                                   MEK double rubs          200+                                                 QUV, hours to 50% loss   960                                                  ______________________________________                                    

We claim:
 1. A curable polyester comprising(a) about 40 to about 100mole percent of residues of 2,6-decalindicarboxylic acid; (b) about 40to about 100 mole percent of residues of 2,2-dimethyl-1,3-propanediol;and any remaining residues comprised of residues of polyols andpolycarboxylic acids; said polyester having a number average molecularweight of from about 1500 to 10,000, a glass transition temperature ofabout 45° C. to about 100° C., and a hydroxy or acid number of from 20to
 100. 2. The polyester of claim 1, wherein the residues of2,6-decalindicarboxylic acid are present in a concentration of 70 to 100mole percent and the residues of 2,2-dimethyl-1,3-propanediol arepresent in a concentation of 70 to 100 mole percent.
 3. The polyester ofclaim 1, wherein the acid or hydroxyl number is 30 to
 80. 4. Thepolyester of claim 1, wherein residues of 2,6-decalindicarboxylic acidare present in a concentration of about 40 to 100 mole percent, residuesof 2,2-dimethyl-1,3-propanediol are present in a concentration of 40 to100 mole percent, and the polyols are selected from the group consistingof hydrogenated bisphenol A, 2,2,4,4-tetramethyl-1,3-cyclobutanediol,1,4-cyclohexanedimethanol and 1,6-hexanediol, and the polycarboxylicacids are selected from the group consisting of isophthalic acid,cyclohexanedicarboxylic acid, terephthalic acid, and2,6-naphthalenedicarboxylic acid.
 5. The curable polyester of claim 1,comprising(a) 40 to 100 mole percent of residues of2,6-decalindicarboxylic acid; 0 to 60 mole percent of residues of acompound selected from the group consisting of naphthalenedicarboxylicacid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylicacid; and (b) 40 to 100 mole percent of residues of2,2-dimethyl-1,3-propanediol; 0 to 50 mole percent of residues ofcyclohexanedimethanol; 0 to 10 mole percent of residues of a compoundselected from the group consisting of trimethylolpropane, glycerol, andtrimellitic anhydride; the total mole percent of (a) being 100 percentand the total mole percent of (b) being 100 percent.
 6. The curablepolyester of claim 1, wherein the acid number is 30 to 80 and thehydroxyl number is less than
 15. 7. The curable polyester of claim 1,wherein the hydroxyl number is 30 to 80, and the acid number is lessthan
 15. 8. The curable polyester of claim 5, wherein the acid number is30 to 80, and the hydroxyl number is less than
 15. 9. The curablepolyester of claim 5, wherein the hydroxyl number is 30 to 80, and theacid number is less than
 15. 10. A thermosetting coating compositioncomprising(I) a curable polyester comprising(a) about 40 to about 100mole percent of residues of 2,6-decalindicarboxylic acid; (b) about 40to about 100 mole percent of residues of 2,2-dimethyl-1,3-propanediol;and any remaining residues comprised of residues of polyols andpolycarboxylic acids; said polyester having a number average molecularweight of from about 1500 to 10,000, a glass transition temperature ofabout 45° C. to about 100° C., and a hydroxy or acid number of from 20to 100; (II) a crosslinking effective amount of a cross-linker reactivewith said polyester.
 11. The composition of claim 10, wherein theresidues of 2,6-decalindicarboxylic acid are present in a concentrationof 70 to 100 mole percent and the residues of2,2-dimethyl-1,3-propanediol are present in a concentation of 70 to 100.12. The composition of claim 10, wherein the acid or hydroxyl number is30 to
 80. 13. The composition of claim 10, wherein residues of2,6-decalindicarboxylic acid are present in a concentration of about 40to 100, residues of 2,2-dimethyl-1,3-propanediol are present in aconcentration of 40 to 100, the polyols are selected from the groupconsisting of hydrogenated bisphenol A,2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,4-cyclohexanedimethanol and1,6-hexanediol, and the polycarboxylic acids are selected from the groupconsisting of isophthalic acid, cyclohexanedicarboxylic acid,terephthalic acid, and 2,6-naphthalenedicarboxylic acid.
 14. Thecomposition of claim 10, comprising(a) 40 to 100 mole percent ofresidues of 2,6-decalindicarboxylic acid; 0 to 60 mole percent ofresidues of a compound selected from the group consisting ofnaphthalenedicarboxylic acid, isophthalic acid, terephthalic acid, andcyclohexanedicarboxylic acid; and (b) 40 to 100 mole percent of residuesof 2,2-dimethyl-1,3-propanediol; 0 to 50 mole percent of residues ofcyclohexanedimethanol; 0 to 10 mole percent of residues of a compoundselected from the group consisting of trimethylolpropane, glycerol, andtrimellitic anhydride; the total mole percent of (a) being 100 percentand the total mole percent of (b) being 100 percent.
 15. The compositionof claim 10, wherein the acid number is 30 to 80 and the hydroxyl numberis less than
 15. 16. The composition of claim 10, wherein the hydroxylnumber is 30 to 80, and the acid number is less than
 15. 17. Thecomposition of claim 14, wherein the acid number is 30 to 80, and thehydroxyl number is less than
 15. 18. The composition of claim 14,wherein the hydroxyl number is 30 to 80, and the acid number is lessthan
 15. 19. The composition of claim 15, wherein the crosslinker is aβ-hydroxyalkylamide.
 20. The composition of claim 15, wherein thecrosslinker is an epoxy-functional compound or resin.
 21. Thecomposition of claim 20, wherein the crosslinker is triglycidylisocyanurate.
 22. The composition of claim 16, wherein the crosslinkeris a blocked isocyanate.
 23. A shaped or formed article coated with thecured composition of claim 10.